A hydrocolloid is a synthetically prepared or naturally occurring polymer capable of forming a thickened gel in the presence of water and polyols.
Hydrogels, hydrocolloids swollen with water or another hydrophilic liquid have been known for the purpose of absorbing or retaining moisture or water. U.S. Pat. Nos. 4,438,258 and 4,552,138 describe typical hydrogels.
In medical applications, hydrogels swollen with water or other liquids generally have good moisture vapor transmission rates. Hydrogels are quite useful for the absorbing or removal of body fluids, such as perspiration, from the pores of the continuous skin of the patient or from a wound, incision or other opening in the skin of the patient.
While certain hydrogels can have some pressure sensitive adhesive properties, the adhesive strength of hydrogels is marginal for general utility skin adhesives. Hydrogels alone are generally not used as medical tapes, dressings, drapes and the like because of lack of good adhesive strength in either dry skin environments ("dry stick adhesion") or in moist skin environments ("wet stick adhesion"). Both of these environments require continuous strong adhesion of a tape, dressing, bandage or the like for proper patient care.
On the other hand, conventional pressure sensitive adhesives have strong dry stick adhesion, but often lack high moisture vapor transmission properties. For this reason, the adhesion may fail in moist environments occurring beneath medical tapes, dressings, drapes and the like.
Also, if antimicrobial agents, such as chlorhexidine, are desired to be administered topically to the skin of the patient, these pressure sensitive adhesives alone are poor candidates to provide rapid delivery of the antimicrobial agent to the skin.
Conventional pressure sensitive adhesives have been mixed with unswollen hydrocolloidal filler material for the purpose of providing wet stick adhesion where initial moist skin environments are common. For example, U.S. Pat. Nos. 4,166,051 and 4,505,976 describe adhesives with hydrocolloids mixed therein. These mixtures are used as sealants about a skin opening of a patient, such as a stoma, following surgery.
A stoma sealant requires wet stick adhesion to absorb or wick away moisture or other body fluids from about the skin opening. However, the use of unswollen hydrocolloidal fillers or reinforcers initially make the adhesive much stiffer and less pliable, reducing the dry stick adhesion of the adhesive against the flexible contours of the movable and stretchable skin.
Furthermore, following the continued absorbance of moisture and other body fluids, inevitably, wet stick adhesion is also reduced. Also such stoma-type adhesives are typically opaque, which, while not important for their usefulness about stomas, limit their usefulness where transparent or nearly transparent adhesives are desired in medical applications such as for incise drapes.
Thus, the use of hydrocolloids in the medical applications has progressed in diverging directions. In one direction, swollen hydrocolloids. Hydrogels provide high moisture vapor transmission rates but without significant dry or wet stick adhesive strength. In the other direction, unswollen hydrocolloids mixed into conventional pressure sensitive adhesives to become opaque stoma-type sealants provide wet stick adhesion at the expense of dry stick adhesion.
What is needed in the art is a composite which has the good dry stick adhesion of a strong pressure sensitive adhesive and the high moisture vapor transmission rate of a swollen hydrocolloid. It is desirable to have a composite which has the capability of avoiding loss of adhesion against the skin or skin opening upon continued exposure to moist conditions. It is also desirable to have an adhesive which has translucency approaching transparency and has the ability to release antimicrobial agents in efficacious amounts when placed in contact with the skin.